An airbed is a large rectangular rubber or plastic bag that is filled with air so that it may be used as a bed. Airbeds are well known in the art and have proven themselves to be very useful. On the one hand, when there is no need to sleep on an inflatable airbed, an owner may simply deflate the airbed (i.e., let all the air out), fold the airbed, and then store the airbed away in a closet or basement. On the other hand, when guests arrive or when the owner of the airbed takes a trip to a place where there is no bed, the owner may simply inflate the airbed and sleep on it.
Most conventional inflatable airbeds have a single chamber, meaning that air can travel anywhere inside the airbed because there is no barrier sealing off one portion of the airbed from another. Therefore, when multiple people sleep or sit on the airbed, air is constantly moved from one portion of the airbed to another as the weight of the person is shifted.
For example, suppose person A is sleeping on the left side of an inflated queen size airbed. Because there is currently no weight on the right side of the airbed, air would naturally flow toward the unweighted right side of the airbed until an equilibrium pressure condition is established (i.e., the right side cannot hold anymore air). This shifting of air to the right side consequently would cause the right side of the airbed to rise.
Next, suppose person B wants to sleep on the now elevated right side of the airbed. As person B descends onto the right side of the airbed, this new weight causes a redistribution of the air back toward the left side of the airbed where person A is sleeping. Air flows back to the left side of the air bed, causing the left side to rise due to the newly added air pressure underneath. This unexpected elevation in the left side of the airbed may even awake person A. Furthermore, each time person A or B moves around during their sleep and causes a shift in weight on the airbed, air may also be shifted around inside the entire airbed. This constant movement of air inside the airbed in response to weight shifts causes different portions of the airbed to rise and fall until the weight movement stops. This constant rocking, elevation or depression of various portions of the airbed every time one person moves can disrupt a good night's sleep.
To address the unequal distribution of air in an airbed, a variety of different constructions have been used to control the structure and shape of airbeds. A first type is an internal I-beam structure, having a material that extends from an interior of a top wall of an airbed to an interior of a bottom wall of the airbed. This structure is designed in such a way to consist of well defined start and stop points, the start and stop points attached to the inner surfaces of the airbed. The I-beam prevents portions of the airbed adjacent to the I-beam from rising beyond a certain height. However, I-beams are inherently weak because of the start and stop points.
An improvement to the I-beam construction is the concept of coil designs. Coils allow for an effectively closed loop to be attached at upper and lower portions of the loop to the interior portions of the upper and lower walls of the airbed. Because a loop is used, there are effectively no start and stop points in this design. Thus, this structure more evenly distributes stress along the inner surfaces of the airbed, and thereby greatly improves the performance and durability of an airbed.
Recently, manufacturers have produced and sold airbeds of greater height or thickness, such that the airbeds more closely resembled a box spring and mattress combination in function and height. This type of an airbed being known as a two layer or a “double high” airbed. Examples of this type of mattress are shown in U.S. Pat. No. 4,547,919 to Wang, U.S. Pat. No. 5,598,593 to Wolfe, and U.S. Pat. No. 6,568,011 to Fisher et al., respectively. As shown in the '011 patent to Fisher et al., the double high airbed is essentially comprised of two stacked single height air mattresses formed with a lower chamber and a separate upper chamber. This is also shown in U.S. Pat. No. 6,073,291 to Davis.
Although this type of double high airbed construction has provided increased comfort levels over single layer or height air mattresses, problems with these known types of mattress construction remain, chief among them being the inability to internally support the mattress so that any internal beams or columns used to form the mattress extend continuously from the bottom face to the top face of the mattress for more uniformly strengthening the mattress, and for more uniformly limiting the expansion or deflection of the mattress faces during use.